The present invention relates to a method of cleaning a fluorine-containing rubber molded article such as a sealing material for semiconductor production apparatuses, the cleaned molded article and semiconductor production apparatuses such as etching equipment which are equipped with the molded article.
In the field of semiconductor industries, sealing materials produced from a silicone material, fluorosilicone material, ethylene/propylene/diene terpolymer (EPDM), and the like have been used generally as molded articles such as sealing materials for semiconductor production apparatuses, and from the viewpoint of excellent heat resistance, plasma resistance and corrosive gas resistance, fluorine-containing rubber materials such as vinylidene fluoride/hexafluoropropylene copolymer rubber, vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer rubber, tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer rubber and tetrafluoroethylene/propylene copolymer rubber have been used for molded articles to be used under particularly strict conditions.
In a production process of semiconductors, there arise organic residues such as photoresist residue, organic solvent residue, synthetic wax and fatty acid derived from human body, inorganic contaminants such as sodium, potassium, gold, iron and copper, and particles. It is important to remove them and not to carry them into the following high temperature heat treating step. Attention is paid particularly to cleaning of a wafer, and strict control on chemicals to be used therefor is demanded.
However for example, since a minimum pattern of 64 Mbit DRAM is 0.35 xcexcm, it is necessary to keep fine particles of as small as about 0.02 xcexcm to about 0.03 xcexcm under control, but the present situation is such that controlling of chemicals to be used for cleaning of wafer up to the above-mentioned level is technically difficult.
The present inventors supposed that only cleaning of semiconductor products such as silicon wafer (article to be processed) by etching and washing is not enough and paid attention to cleaning of molded members as components of semiconductor production apparatuses, particularly sealing materials thereof.
The reason why attention was paid to the molded articles such as sealing materials to be used on semiconductor production apparatuses was that particles and metal components are considered to possibly adhere to a surface of semiconductor, thereby causing lowering of yield.
As a method of cleaning the molded articles such as sealing materials, there have been usually employed, for example, a method of wiping them with an absorbent cotton impregnated with a solvent such as isopropyl alcohol. However it is still impossible to sufficiently reduce an amount of particles adhering to the molded articles and a content of metal components, and even if the above-mentioned chemicals used for cleaning of wafer, etc. are used, cleaning enough to cope with high integration of semiconductors and fine patterning has not yet been achieved.
In view of the above-mentioned fact, objects of the present invention are to provide a novel and effective cleaning method capable of giving cleaned fluorine-containing rubber molded articles for semiconductor production apparatuses, and further to provide semiconductor production apparatuses which can reduce sufficiently particles and metal components resulting from molded articles such as sealing materials.
The present invention relates to the method of cleaning a fluorine-containing rubber molded article for semiconductor production apparatuses, which comprises washing the fluorine-containing rubber molded article once or two or more times preferably at a temperature of not less than 80xc2x0 C. with ultra pure water which has a metal content of not more than 1.0 ppm and does not contain fine particles of not less than 0.2 xcexcm in an amount of more than 300 per 1 ml.
The present invention also relates to the method of cleaning a fluorine-containing rubber molded article for semiconductor production apparatuses, which comprises washing the fluorine-containing rubber molded article once or two or more times with an organic compound or inorganic compound which has a metal content of not more than 1.0 ppm, does not contain fine particles of not less than 0.5 xcexcm in an amount of more than 200 per 1 ml and is in liquid form at a washing temperature.
Further the present invention relates to the fluorine-containing rubber molded article for semiconductor production apparatuses which is subjected to cleaning by dry etching.
Further the present invention relates to the method of cleaning a fluorine-containing rubber molded article for semiconductor production apparatuses, which comprises extraction cleaning.
Further the present invention relates to the method of cleaning a fluorine-containing rubber molded article for semiconductor production apparatuses, in which after a method of washing with an organic compound or inorganic compound having an oxidizing ability and a method of washing with an inorganic compound having a high ability of dissolving a metal are carried out in this order or in reverse order, washing with ultra pure water is conducted and then removal of water is carried out in a clean inert gas or air. Still further the present invention relates to the method of cleaning a fluorine-containing rubber molded article for semiconductor production apparatuses, in which after washing with an aqueous solution of a mixture of H2SO4 and H2O2 which has a metal content of not more than 1.0 ppm and does not contain fine particles of not less than 0.5 xcexcm in an amount of more than 200 per 1 ml is carried out, washing with an aqueous solution of HF which has a metal content of not more than 1.0 ppm and does not contain fine particles of not less than 0.5 xcexcm in an amount of more than 200 per 1 ml, washing with ultra pure water which has a metal content of not more than 1.0 ppm and does not contain fine particles of not less than 0.2 xcexcm in an amount of more than 300 per 1 ml and then removing of water in a clean inert gas or air which does not contain fine particles of not less than 0.2 xcexcm in an amount of more than 26 per 1 liter and has a content of organic component (TOC) of not more than 0.1 ppm are carried out.
Further the present invention relates to the fluorine-containing rubber molded article for semiconductor production apparatuses, in which the number of particles of not less than 0.2 xcexcm being present on the surface thereof is not more than 200,000/cm2.
Further the present invention relates to the fluorine-containing rubber molded article for semiconductor production apparatuses, in which the molded article is subjected to cleaning by one of the above-mentioned cleaning methods or by a combination of two or more thereof and the number of particles of not less than 0.2 xcexcm being present on the surface thereof is not more than 200,000/cm2.
The present invention also relates to the semiconductor production apparatuses equipped with the above-mentioned fluorine-containing rubber molded article, for example, etching equipment, washing equipment, exposure equipment, grinding equipment, film forming equipment and ion diffusion and implantation equipment.
Firstly the fluorine-containing rubber constituting the fluorine-containing rubber molded article for semiconductor production apparatuses of the present invention is explained below.
Non-restricted examples of the fluorine-containing rubber constituting the fluorine-containing rubber molded article for semiconductor production apparatuses of the present invention are those which have been used for molding materials for sealing materials nd the like. For example, there are a copolymer rubber represented by the formula (1): 
wherein m is from 85 to 60, n is from 15 to 40, or the formula (2): 
wherein m is from 95 to 50, n is from 5 to 50, Rf is a perfluoroalkyl group having 1 to 8 carbon atoms,
a terpolymer rubber represented by the formula (3): 
wherein 1 is from 85 to 20, m is from 0 to 40, n is from 15 to 40,
a terpolymer rubber represented by the formula (4): 
wherein 1 is from 95 to 45, m is from 0 to 10, n is from 5 to 45, X, Y and Z are individually fluorine atom or hydrogen atom, Rf is a perfluoroalkyl group having 1 to 8 carbon atoms,
a terpolymer rubber represented by the formula (5): 
wherein 1 is from 95 to 35, m is from 0 to 30, n is from 5 to 35, Rf is a perfluoroalkyl group having 1 to 8 carbon atoms, and the like. Among them, from the viewpoint of chemical resistance, heat resistance and plasma resistance, it is preferable to use the copolymer rubbers represented by the formulae (1) and (2) and the terpolymer rubber represented by the formula (3).
Further as the fluorine-containing rubber constituting the fluorine-containing rubber sealing material in the present invention, there are copolymers comprising an elastomeric segment copolymer and a non-elastomeric segment copolymer.
The elastomeric segment represents a non-crystalline segment having a glass transition temperature of not more than 25xc2x0 C. Example of the preferred components is, for instance, TFE/PAVE/monomer giving a curing site (45 to 90/10 to 50/0 to 5 in % by mole, hereinafter the same), more preferably 45 to 80/20 to 50/0 to 5, especially 53 to 70/30 to 45/0 to 2.
Examples of the monomer giving a curing site are, for instance, vinylidene fluoride, iodine-containing monomer represented by CX2=CXxe2x80x94Rf3CHRI, in which X is H, F or CH3, Rf3 is a fluoroalkylene group, perfluoroalkylene group, fluoropolyoxyalkylene group or perfluoropolyoxyalkylene group, R is H or CH3, nitrile group-containing monomer represented by 
wherein m is from 0 to 5, n is from 1 to 3, bromine-containing monomer, and the like. Usually the iodine-containing monomer, etc. are suitable.
Examples of the non-elastomeric segment copolymer are:
(1) VdF/TFE (0 to 100/100 to 0), particularly VdF/TFE (70 to 99/30 to 1), PTFE or PVdF;
(2) ethylene/TFE/HFP (6 to 43/40 to 81/10 to 30), 3,3,3-trifluoropropylene-1,2-trifluoromethyl-3,3,3-trifluoropropylene-1/PAVE (40 to 60/60 to 40);
(3) TFE/CF2=CFxe2x80x94Rf1 (amount exhibiting non-elastomeric property, namely not more than 15% by mole of CF2=CFxe2x80x94Rf1, in which Rf1 is CF3 or ORf2, Rf2 is a perfluoroalkyl group having 1 to 5 carbon atoms);
(4) VdF/TFE/CTFE (50 to 99/30 to 0/20 to 1);
(5) VdF/TFE/HFP (60 to 99/30 to 0/10 to 1);
(6) ethylene/TFE (30 to 60/70 to 40);
(7) polychlorotrifluoroethylene (PCTFE);
(8) ethylene/CTFE (30 to 60/70 to 40);
and the like. Among them, from the viewpoint of chemical resistance and heat resistance, non-elastomeric copolymers such as PTFE and TFE/CF2=CFxe2x80x94Rf1 are particularly preferable.
The above-mentioned fluorine-containing rubber can be prepared by the molding methods such as compression molding and injection molding.
Then the first method of cleaning the fluorine-containing rubber molded article for semiconductor production apparatuses according to the present invention is explained below.
The first cleaning method of the present invention is the method of cleaning the fluorine-containing rubber molded article for semiconductor production apparatuses, which comprises washing the fluorine-containing rubber molded article once or two or more times with ultra pure water which has a metal content of not more than 1.0 ppm and does not contain fine particles of not less than 0.2 xcexcm in an amount of more than 300 per 1 ml.
The xe2x80x9cultra pure waterxe2x80x9d means water which has a metal content of not more than 1.0 ppm and does not contain fine particles of not less than 0.2 xcexcm in an amount of more than 300 per 1 ml. From the viewpoint of reduction of mixing of metals into a sealing material and reduction of adherence of fine particles onto a molded article, it is preferable that the metal content is not more than 0.8 ppm and the number of fine particles of not less than 0.2 xcexcm is 250 or less per 1 ml, especially the metal content is not more than 0.5 ppm and the number of fine particles of not less than 0.2 xcexcm is 200 or less per 1 ml.
Examples of impurity metals in ultra pure water are, for instance, Na, Fe, Cr, As, Al, Ba, and the like, and the fine particles mean algae, secretion of microorganisms in water, dead microorganisms, dust in the air, and the like.
The ultra pure water can be prepared by taking the steps from dechlorination of raw water, reverse osmosis (Ro) treatment, membrane treatments such as cartridge type water purifier, ultrafiltration (UF) and microfiltration (MF), sterilization by ultraviolet rays through deaeration treatment, thereby increasing purity and removing microorganisms, fine particles and organic substances.
The method of washing of the first cleaning method is not limited particularly, and it is preferable to carry out washing by showering, spraying, jet-scrubbing, dipping or ultrasonic or megasonic cleaning. Also it is preferable to carry out cleaning with boiling water from the point that fine particles can be removed effectively and efficiently.
Washing is conducted once or two or more times. The number of washing steps is not particularly limited as far as the number of particles having a specific particle size on a surface of cleaned molded article is in the range specified hereinafter. The washing may be carried out once in case of a combination with other cleaning methods. In case of the first cleaning method only, it is preferable to carry out the washing two or more times.
In the first cleaning method, from the viewpoint of enhancing removal efficiency of particles, a temperature of ultra pure water at washing is preferably from 20xc2x0 to 100xc2x0 C., especially 40xc2x0 to 100xc2x0 C. From the point that fine particles can be removed effectively and efficiently, it is preferable to carry out washing with boiling water. A boiling water temperature is from 70xc2x0 to 100xc2x0 C., preferably 80xc2x0 to 100xc2x0 C., especially 90xc2x0 to 100xc2x0 C. A boiling time is from 0.5 to 5 hours. At the time of washing with boiling water, from the viewpoint of effective use of ultra pure water, it is preferable that ultra pure water is subjected to refluxing.
An atmosphere is not limited particularly. However from the viewpoint of preventing fine particles from mixing, it is preferable to carry out the washing in an atmosphere in clean room, clean bench, clean tunnel, and the like.
The first method of cleaning with ultra pure water is also capable of removing other contaminants, and is particularly suitable as a method for removing ions such as Fxe2x88x92, SO42xe2x88x92 and Clxe2x88x92 which are contained in or adhered to the fluorine-containing rubber molded article.
It is possible to not only reduce water content but also remove organic components contained in the air and adhered to the molded article, by heat-treating, after the washing, usually in a cleaned inert gas atmosphere such as nitrogen gas, argon gas or helium gas or by flowing the inert gas at 50xc2x0 to 300xc2x0 C., preferably 100xc2x0 to 250xc2x0 C. for 1 to 72 hours, preferably 1 to 24 hours.
Usually a particle size of particles on the surface of fluorine-containing rubber molded article is not less than 0.2 xcexcm, and 500,000 to 1,000,000 particles/cm2 are present on the surface of molded article. On the contrary, the number of particles having a particle size of not less than 0.2 xcexcm and being present on the surface of fluorine-containing rubber molded article cleaned by the above-mentioned first cleaning method is not more than 100,000/cm2. The number of particles having a particle size of not less than 0.2 xcexcm is preferably not more than 50,000/cm2, especially not more than 20,000/cm2. It is a matter of course that the number of particles having a particle size exceeding 0.5 xcexcm is as few as possible, preferably not more than 10,000/cm2, especially 5,000/cm2.
Herein particles mean dusts mixed in each production step of molded article, processing aids such as a releasing agent and organic residues such as fatty acid derived from human body. It is preferable to use a vessel laminated with a fluorine-containing resin film or polyethylene resin film, a vessel made of fluorine-containing rein and a vessel made of polyethylene so that the molded article should not come into contact with a metal.
Then methods of measuring a size and the number of particles being present on the surface of the cleaned fluorine-containing rubber molded article and methods of evaluation thereof are explained below.
In the present invention, the molded article is dipped in water, and the size and the number of particles coming out of the molded article into water are measured by the methods mentioned below. The measuring methods are roughly classified into a direct method and an indirect method. The direct method is a method of counting the number of particles in water by a particle size, and the indirect method is a method of indicating a degree of blockage of a specific membrane filter for evaluation.
Herein the measuring method represented by the direct method is explained below in detail. As the direct method, there are three methods, i.e. {circle around (1)} direct microscopic method, {circle around (2)} electron microscopic method and {circle around (3)} fine particle meter method.
In the method {circle around (1)}, water is passed through a membrane filter and particles caught on the surface of the membrane filter are observed and measured with an optical microscope. The method {circle around (2)} is nearly the same as the method {circle around (1)}, but measurement is done by using a scanning electron microscope instead of the optical microscope. In the method {circle around (3)}, the number and size of particles are measured by emitting light to water containing particles and flowed into a sensor part and then measuring electrically amounts of transmitted light and scattered light with a particle counter.
Then the second method of cleaning the fluorine-containing rubber molded article for semiconductor production apparatuses according to the present invention is explained.
The second cleaning method of the present invention is the method of cleaning the fluorine-containing rubber molded article for semiconductor production apparatuses, which comprises washing the fluorine-containing rubber molded article once or two or more times with an organic compound or inorganic compound which has a metal content of not more than 1.0 ppm, does not contain fine particles of not less than 0.5 xcexcm in an amount of more than 200 per 1 ml and is in liquid form at a washing temperature.
Examples of the organic compound in the form of liquid which is used for the second cleaning method of the present invention are, for instance, ketones such as acetone and methyl ethyl ketone; alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol; hydrocarbons such as hexane, octane and xylene; chlorine-based hydrocarbons such as trichloroethylene, tetrachloroethylene and carbon tetrachloride; fluorine-based hydrocarbons such as perfluorobenzene, perfluorohexane and 1,1-dichloro-1-fluoroethane; ethers such as diethyl ether; esters such as methyl acetate and ethyl acetate; and the like. Those compounds can be used in optional combination thereof.
Examples of the inorganic compound in the form of liquid are, for instance, H2SO4, HNO3, H2O2, HF, O3 (aqueous ozone solution), NH4OH, HCl , and the like. Those compounds can be used in an optional combination thereof. Particularly a solution of H2SO4/H2O2 mixture, a solution of HCl/H2O2 mixture, a solution of O3/HF mixture, a solution of O3/H2SO4 mixture, a solution of O3/HCl mixture, an aqueous solution of HF are usually used in semiconductor production process, and are suitable as a cleaning solution.
A metal content of the above-mentioned organic compound or inorganic compound in the form of liquid which is used in the second cleaning method of the present invention is not more than 1.0 ppm. From the point of reduction of metal mixing in the molded article, the metal content is preferably not more than 0.8 ppm, especially not more than 0.5 ppm.
Metals which may be contained in the above-mentioned organic compound or inorganic compound in the form of liquid are Na, Fe, Cr, As, Al, Ba, and the like.
Also the above-mentioned organic compound or inorganic compound in the form of liquid does not contain fine particles of not less than 0.5 xcexcm in an amount of more than 200 per 1 ml from the viewpoint of reduction of adhering amount of fine particles onto the molded article. The number of fine particles of not less than 0.5 xcexcm is preferably not more than 150 per 1 ml, especially not more than 100 per 1 ml.
The fine particles which may be contained in the above-mentioned organic compound or inorganic compound in the form of liquid mean dusts in the air, fine particles to be mixed in the production process, fine particles adhering to an inner wall of a storage vessel, a processing aid contained in the inner wall of a storage vessel, and the like.
In order to satisfy the above-mentioned requirements, a temperature of the above-mentioned organic compound or inorganic compound in the form of liquid at the time of washing is preferably not less than 20xc2x0 C. and less than its boiling point.
As the organic compound or inorganic compound in the form of liquid, compounds which are commercially available and have a grade for electronic industries can be used.
An object of the second cleaning method is roughly classified into two. One is to remove impurity organic components by an inorganic compound or organic compound having an oxidizing ability. For that purpose, inorganic compounds such as a solution of H2SO4/H2O2 mixture and an aqueous solution of O3; organic compounds such as acetone, methyl ethyl ketone and isopropyl alcohol are suitable. Another object is to remove impurity metal components by an inorganic compound having a strong ability of dissolving metals. For this purpose, inorganic acids such as HF, HCl, H2SO4 and HNO3 and the above-mentioned solution of H2SO4/H2O2 mixture are suitable.
The method of washing of the second cleaning method is not limited particularly, and it is preferable to carry out washing by showering, spraying, jet-scrubbing, dipping or ultrasonic or megasonic cleaning. Also it is preferable to carry out washing by boiling from the point that fine particles can be removed effectively and efficiently. A boiling temperature is from 70xc2x0 to 100xc2x0 C., preferably 80xc2x0 to 100xc2x0 C. A boiling time is from 0.5 to 5 hours. At the time of washing by boiling, from the viewpoint of effective use of the inorganic compound or organic compound, it is preferable that the inorganic compound or organic compound in the form of liquid is subjected to refluxing.
In the second cleaning method, an atmosphere at washing is not limited particularly. However from the viewpoint of preventing fine particles from mixing, it is preferable to carry out the washing in an atmosphere in clean room, clean bench, clean tunnel, and the like.
The number of washing steps is not particularly limited as far as the number of particles on a surface of cleaned molded article is in the range specified hereinafter. Washing may be conducted plural times. Also the washing with ultra pure water which is explained in the first cleaning method may be carried out once or two or more times before and/or after the second cleaning method. Further it is preferable to carry out the heat treatment after the washing which is explained in the first cleaning method.
The number of particles having a particle size of not less than 0.2 xcexcm and being present on the surface of fluorine-containing rubber molded article cleaned by the above-mentioned second cleaning method of the present invention is not more than 100,000/cm2. From the viewpoint of a decrease in the number of particles to be generated, the number of particles having a particle size of not less than 0.2 xcexcm is preferably not more than 50,000/cm2, especially not more than 20,000/cm2.
The methods of measuring a size and the number of particles being present on the surface of the cleaned fluorine-containing rubber molded article and methods of evaluation thereof are the same as in the above-mentioned first cleaning method.
Then the cleaning by dry etching which is employed in the third cleaning method of the present invention is explained. Generally the cleaning by dry etching is a method of chemically and/or physically decomposing particles being present on the surface of articles to be cleaned by bringing a gas having a high chemical reactivity, excited gas or light into contact with the articles.
As the cleaning method by dry etching, there are methods of UV/O3 irradiation, ion beam irradiation, laser beam irradiation, plasma irradiation and gas etching.
Namely the third cleaning method of the present invention is a method of cleaning of the fluorine-containing rubber molded article for semiconductor production apparatuses by dry etching by UV/O3 irradiation, ion beam irradiation, laser beam irradiation, plasma irradiation or gas etching.
The third cleaning method of the present invention is suitable particularly for removal of impurity organic components.
Those methods of cleaning by dry etching are explained below.
(1) Cleaning Method with UV/O3 
The cleaning with UV/O3 is a method of irradiating ultraviolet rays to an article to be cleaned to directly decompose or activate an organic substance adhering on its surface, then easily subjecting to oxidization, and at the same time to decompose and modify the impurity organic substance into a volatile substance by an action of activated oxygen separated from ozone generated by an action of ultraviolet rays. Thus the impurity organic substance is removed. For example, UV/O3 cleaning equipment commercially available from Eye Graphics Co., Ltd., Ushio Inc., etc. can be used suitably.
(2) Cleaning Method by Ion Beam
The cleaning by ion beam is a physical etching method for removing particles by accelerating charged particles such as argon ions in a low pressure chamber, taking out the ion beam and then irradiating the beams against the article to be cleaned, thus removing particles. Ion beam etching equipment is commercially available from IONTECH CO., LTD., etc., and the commercially available equipment can be used suitably in the present invention.
(3) Cleaning Method by Laser Beam
The cleaning by laser beam is a method of cleaning by irradiating high performance ruby laser pulses against the article to be cleaned. Equipment for laser beam etching is also available commercially, and can be used suitably in the present invention.
(4) Cleaning Method by Plasma
Cleaning by plasma is a method of cleaning by utilizing an active oxygen plasma generated by introducing oxygen gas into high frequency electric field. According to this method, an organic substance is oxidized and finally converted to CO2 and H2O and exhausted for removal. Plasma ashing equipment to be used for the cleaning by plasma is commercially available, and can be used suitably in the present invention.
(5) Cleaning Method by Gas Etching
A gas to be used suitably for the cleaning by gas etching is a hydrofluoric anhydride gas. An aimed substance is removed by properly adjusting a pressure and temperature. In this method, fluorine gas, ozone gas, hydrofluoric anhydride gas are used, and among them, a mixed gas of hydrofluoric anhydride gas, anhydrous fluorine gas and ozone gas is suitable. Particles can be removed by bringing those gases into contact with an article to be cleaned and properly adjusting a pressure and temperature of an atmosphere.
Then the fourth cleaning method of the present invention is a method of cleaning the fluorine-containing rubber molded article for semiconductor production apparatuses by extraction cleaning of the fluorine-containing rubber molded article.
The fourth cleaning method is suitable particularly for removing impurity organic components.
Examples of the extraction cleaning method in the present invention are Soxhlet extraction cleaning, high temperature high pressure extraction cleaning, microwave extraction cleaning and supercritical extraction cleaning. Those extraction cleaning methods are explained below.
(1) Soxhlet Extraction Cleaning Method
This extraction cleaning is carried out by using a device equipped with a circulating type cooler, extraction tube and solvent flask. A sample is put in the extraction tube, and an upper end of the tube is connected to the cooler and a lower end thereof is connected to the flask charged with a solvent. The device is so designed that the extraction tube is provided with a side tube playing a role as a siphon, and when the solvent in the flask is heated, steam generated goes up through the side tube, is condensed in the cooler to become a liquid and is dropped onto the sample, and when the dropped liquid reaches a top level of the siphon, it returns to the flask through the side tube, thus carrying out the extraction.
(2) High Temperature High Pressure Extraction Cleaning Method
This is a method of extracting by using a solvent. The extraction is carried out by bringing the solvent into contact with a sample at high temperature at high pressure.
(3) Microwave Extraction Cleaning Method
A microwave is emitted to the solvent to rapidly heat it. The extraction is carried out with the heated solvent. Equipment for this method is also commercially available, and can be used suitably in the present invention.
(4) Supercritical Extraction Cleaning Method
Supercritical extraction is an equilibrium separation method, in which a supercritical liquid (high density gas) to be used as a separating solvent is brought into contact with a substance to be separated (particles) and a difference in solubility of the components to be extracted in the solvent is used. Generally CO2 gas is used as a supercritical fluid, and in addition, fluid gases such as ethane, N2O and water are used. Also to enhance extraction of polar substances, in many cases, a mixed liquid to which alcohol, ketone or the like is added in an amount of several percents is used. Equipment used for this method is also commercially available, and can be used suitably in the present invention.
After the cleaning treatment, the above-mentioned heat-treatment may be carried out.
The number of particles of not less than 0.2 xcexcm being present on the surface of the fluorine-containing rubber molded article cleaned by those dry etching methods or extraction cleaning methods is not more than 100,000/cm2, preferably not more than 50,000/cm2, especially not more than 20,000/cm2.
The above-mentioned first, second, third and fourth cleaning methods of the present invention can be used in an optional combination thereof.
While the features of each cleaning method are explained above, mentioned below are explanation on the cleaning methods of the present invention classified by items to be removed (purpose of cleaning).
Firstly examples of the particularly effective method (A) of removing organic components contained in the air and causing an organic gas and impurity organic components such as a releasing agent used at molding are the following four cleaning methods.
(A-1) The second cleaning method employing an inorganic compound having an oxidizing ability
(A-2) The second cleaning method employing an organic compound having an oxidizing ability
(A-3) The third cleaning method by dry etching
(A-4) The fourth extraction cleaning method
Those methods may be used solely or in a combination of two or more thereof. In case of the combination use, an order of cleaning methods may be optionally selected.
Subsequently the particularly effective method (B) for removing impurity metal components is the second cleaning method using an inorganic compound having an excellent ability of dissolving metal components.
Also the particularly effective method (C) for removing impurity ions (for example, Fxe2x88x92, SO42xe2x88x92, Clxe2x88x92) is the first cleaning method using ultra pure water.
Further generation of water can be reduced by a drying step for removing water after carrying out those cleaning methods. As the method (D) used for the drying step, there are, for example, a method of drying in an atmosphere or stream of clean inert gas such as nitrogen gas or in vacuum; a method of drying by blowing clean dry air from which organic substances and fine particles have been removed; and the like method.
The clean inert gas or air to be used for the drying (removal of water) means gas or air which has a content of organic components (TOC) of not more than 0.1 ppm and does not contain fine particles of not less than 0.2 xcexcm in an amount of more than 26 per 1 liter (This is an environment of so-called class 100).
In order to remove all the above-mentioned impurities effectively, it is desirable to carry out the above-mentioned methods (A) to (D) in the order of (A)xe2x86x92(B)xe2x86x92(C)xe2x86x92(D) or (B)xe2x86x92(A)xe2x86x92(C)xe2x86x92(D). In the cleaning method (A), one of the methods (A-1) to (A-4) or a combination of two or more thereof may be employed.
Particularly in case of sealing materials for semiconductor, and the like, where a decrease in the number of particles, a decrease in an amount of ions, a reduction of generation of organic gas and a reduction of generation of water are demanded strongly, it is particularly preferable to combine cleaning with a solution of H2SO4/H2O2 mixture and cleaning with an aqueous solution of HF and further carry out cleaning with boiled ultra pure water and then drying by heating in a clean inert gas stream.
The fluorine-containing rubber molded article cleaned by those methods can be suitably used as a molded article such as a sealing material for production apparatuses in semiconductor industries where scale down is further accelerated and cleanliness is demanded.
Examples of the sealing material are O-ring, square ring, gasket, packing, oil seal, bearing seal, lip seal, and the like. In addition, the molded article can be used for various elastomer products such as diaphragm, tube, hose and various rubber rolls, and also can be used as a coating material and lining material.
In the present invention, the semiconductor production apparatuses are not limited particularly to equipment for producing semiconductors, but widely includes whole production apparatuses used in the field of semiconductor where high cleanliness is demanded, such as equipment for producing liquid crystal panel and plasma panel.
The fluorine-containing rubber molded article can be used built in the following semiconductor production apparatuses.
Dry etching equipment
Plasma etching device
Reactive ion etching device
Reactive ion beam etching device
Sputter etching device
Ion beam etching device
Wet etching equipment
Ashing equipment
Dry etching cleaning equipment
UV/O3 cleaning device
Ion beam cleaning device
Laser beam cleaning device
Plasma cleaning device
Gas etching cleaning device
Extraction cleaning equipment
Soxhlet extracting cleaning device
High temperature high pressure extracting cleaning device
Microwave extracting cleaning device
Supercritical extracting cleaning device
Stepper
Coater developer
CMP equipment
CVD equipment
Sputtering equipment
Oxidation diffusion equipment
Ion implantation equipment